Implement MappedShuffle for tracking the permutation of an array

src/gtest/test_random.cpp

@@ -0,0 +1,34 @@
+#include <gtest/gtest.h>
+
+#include "random.h"
+
+int GenZero(int n)
+{
+    return 0;
+}
+
+int GenMax(int n)
+{
+    return n-1;
+}
+
+TEST(Random, MappedShuffle) {
+    std::vector<int> a {8, 4, 6, 3, 5};
+    std::vector<int> m {0, 1, 2, 3, 4};
+
+    auto a1 = a;
+    auto m1 = m;
+    MappedShuffle(a1.begin(), m1.begin(), a1.size(), GenZero);
+    std::vector<int> ea1 {4, 6, 3, 5, 8};
+    std::vector<int> em1 {1, 2, 3, 4, 0};
+    EXPECT_EQ(ea1, a1);
+    EXPECT_EQ(em1, m1);
+
+    auto a2 = a;
+    auto m2 = m;
+    MappedShuffle(a2.begin(), m2.begin(), a2.size(), GenMax);
+    std::vector<int> ea2 {8, 4, 6, 3, 5};
+    std::vector<int> em2 {0, 1, 2, 3, 4};
+    EXPECT_EQ(ea2, a2);
+    EXPECT_EQ(em2, m2);
+}